Semiconductor chips, in particular power semiconductor chips, are often mounted on a circuit carrier by way of a diffusion solder connection. The semiconductor chip is provided with a metallization having an outer layer made of a diffusion solder. A connection between the semiconductor chip and the circuit carrier is produced by the formation of intermetallic phases at the boundary between the diffusion solder layer and the surface of the circuit carrier.
The intermetallic phases formed have a higher melting point than the melting point of the diffusion solder. Consequently, the production temperature of the connection is lower than the melting point of the connection formed. A diffusion solder connection thus has the advantage that it is thermally stable, and in particular thermally stabler than a soft solder connection. A diffusion solder connection is thus advantageous particularly in the case of power semiconductor devices.
A diffusion solder layer is typically provided as the outermost layer of a multilayer metallization on the semiconductor chip. DE 101 24 141 discloses a metallization having at least four layers. A buffer layer made of aluminum, a diffusion barrier layer, at least one adhesion promoter layer and a diffusion solder layer are provided.
This metallization structure is complicated and costly to produce. This metallization also has the disadvantage that the production of a connection between the semiconductor chip and the circuit carrier may be unreliable.